The invention relates generally to ink cartridges for computer controlled printers and, more specifically, to apparatus for refilling collapsible ink bags within such cartridges.
Computer-controlled printers are well known and replaceable pen and ink cartridges for such printers are likewise well known. These cartridges contain an ink reservoir bag which is maintained at sub-atmospheric pressure to minimize the likelihood of ink inadvertently leaking therefrom. One such printer and the ink cartridges for it are described in Hewlett-Packard Journal, February 1994, Volume 45, Number 1.
The ink delivering nozzle of the cartridge assembly normally remains primed by ink so that it is ready to print on demand and remains so as ink is withdrawn. The ink bag progressively collapses as ink is expelled therefrom. De-priming of the nozzle occurs substantially only when the ink volume is exhausted.
One example of a prior art ink replenishment system includes a double-septum needle (nozzle) arrangement which requires a number of parts and which is therefore comparatively expensive to manufacture. A dual mechanical valving set-up as found on compressed gas cylinders has also been used as have three way valves. All of these prior art techniques for ink replenishment are relatively complex, expensive and bulky.
The manner in which the invention deals with the prior art disadvantage to produce a novel and advantageous new combination will be evident as this specification proceeds.